The present invention relates generally to inkjet printers. More specifically, the present invention relates to a method and apparatus for removing water from printed sheets.
An inkjet printer includes one or more printer cartridges for depositing swaths of ink dots on a print medium. The ink dots are deposited in a controlled manner to produce text and images.
A thermal inkjet printer cartridge includes a housing and a printhead. The housing holds a reservoir of ink, which may be water-based. The printhead draws small quantities of ink from the reservoir, rapidly heats the small quantities of ink beyond boiling, and ejects the small quantities of ink through nozzles. The ejected ink is deposited on the print medium. Water in the ink is absorbed by a print medium such as paper.
High-throughput printers usually include dryers for removing water from the print medium. A typical dryer includes a glass bulb that generates infrared radiation, which heats the water and causes the water to evaporate.
However, the bulbs are expensive. Moreover, the infrared radiation heats the print medium and the ink, as well as the water. Discoloration (e.g., xe2x80x9cbrowningxe2x80x9d) of the print medium can occur.
Low-throughput printers usually do not include dryers. The dryers are too expensive. Instead, the print medium is allowed to dry after being ejected from the printer. If the print medium is handled before it has dried, the ink can be smeared.
Moreover, if the water is not removed within ten to twenty seconds after the ink has been deposited, the water can cause the print medium to xe2x80x9ccockle.xe2x80x9d Cockling occurs when the water is absorbed into cellulose fibers of the print medium. The water causes the fibers to swell and generate localized expansions. The localized expansions cause the print medium to warp and wrinkle. Warping and wrinkling can reduce print quality and overall appearance of the print medium.
There is a need for an inexpensive dryer for inkjet printers. There is also a need for a dryer that does not cause discoloration of the print medium.
These needs are met by the present invention. According to one aspect of the present invention, a printer includes a print medium path and a microwave dryer located along the print medium path. According to another aspect of the present invention, water may be removed by applying evanescent microwaves to a print medium.
Other aspects and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the present invention.